This invention relates to an article for joining dimensionally recoverable parts, and in particular to a patch for joining overlapping edges of a dimensionally recoverable cover.
A dimensionally recoverable article is an article the dimensional configuration of which may be made substantially to change when subjected to treatment. Usually these articles recover towards an original shape from which they have previously been deformed but the term "recoverable", as used herein, also includes an article which adopts a new configuration, even if it has not been previously deformed.
A typical form of dimensionally recoverable article is a heat recoverable article, the dimensional configuration of which may be changed by subjecting the article to heat treatment. In their most common form, heat recoverable articles comprise a shrinkable sleeve made from a polymeric material.
In the production of heat recoverable articles, the polymeric material may be cross-linked at any stage in the production of the article that will enhance the desired dimensional recoverability. One manner of producing a heat-recoverable article comprises shaping the polymeric material into the desired heat-stable form, subsequently cross-linking the polymeric material, heating the article to a temperature above the crystalline melting point or, for amorphous materials the softening point, as the case may be, of the polymer, deforming the article and cooling the article whilst in deformed state so that the deformed state of the article is retained. In use, since the deformed state of the article is heat-unstable, application of heat will cause the article to assume its original heat-stable shape.
In other articles, as described, for example, in British Pat. No. 1,440,524, an elastomeric member such as an outer tubular member is held in a stretched state by a second member, such as an inner tubular member, which, upon heating weakens and thus allows the elastomeric member to recover.
Recoverable articles are frequently used to cover objects having a tubular or otherwise regular elongate configuration, to provide, for example, environmental sealing protection. Where no free end of the elongate object is available, it is common practice to use a so-called wrap-around article, that is an article, typically in the form of a sheet, that is installed by wrapping it around the object to be covered so that opposed longitudinal edges overlap. In order to hold the wraparound article around the object a closure means is applied to secure together the opposed longitudinal edges.
It is known from U.S. Pat. No. 4,200,676 (Raychem Corporation) to use, as a closure means for a wrap-around article, a laminar strip, known as a "patch closure", comprising layer of a cross-linked hot melt adhesive coated on one surface of a reinformced polymer layer. The patch strip is positioned along the closure line and the layer of adhesive activated by heating to provide a secure bond between the overlapping edges of the wraparound article.
Another known wrap-around article is described in European patent application Publication No. 100170 (Shaw Industries Ltd). It comprises a single sheet layer of heat-shrinkable polyolefin material. Overlapping edges of the wrapped sheet are held together simply by heating the sheet to cause the edges to weld to each other. No separate patch is used.